<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>set and map</title>
		<script>
			var a=new Set();
			a.add("dog");
			a.add("pig");
			a.add("cat");
			a.add("dog");
			console.dir(a);
			//var b=new Map()
		</script>
	</head>
	<body>
	</body>
</html>